<template>
  <div>
    <p>请选择你要购买的书籍</p>
    <ul>
      <li v-for ='(item,ind) in arr' :key='ind'>
        <span>{{item['name']}}</span>
        <button @click="buy(ind)">买书</button>
      </li>
    </ul>
    <table border="1" width="500" cellspacing="0">
      <tr>
        <th>序号</th>
        <th>书名</th>
        <th>单价</th>
        <th>数量</th>
        <th>合计</th>
      </tr>
      <tr v-for='(item,index) in arr' :key='index'>
         <td>{{index +1}}</td>
         <td>{{item['name']}}</td> 
         <td>{{item['price']}}</td>
         <td>{{item['count']}}</td>
         <td>{{item['price'] * item['count']}}</td>
      </tr>
     
    </table>
    <p>总价格为:{{allPrice}} </p>
  </div>
</template>

<script>
export default {
  data() {
    return {
      arr: [
        {
          name: "水浒传",
          price: 107,
          count: 0,
        },
        {
          name: "西游记",
          price: 192,
          count: 0,
        },
        {
          name: "三国演义",
          price: 219,
          count: 0,
        },
        {
          name: "红楼梦",
          price: 178,
          count: 0,
        },
      ],
    };
  },
  methods: {
    buy(index) {
      this.arr[index]['count'] ++;
    }
  },
  computed: {
    allPrice() {
      return this.arr.reduce((sum, obj)=> {
        return (sum+= obj['price'] *obj['count']) 
      },0)
    }
  }
};
</script>``